Of 12 patients with relapsed CD20(+) B-cell
non-Hodgkin's lymphoma (B-NHL) enrolled in a phase I study of
rituximab, 11 were eligible, and of these 2 achieved a complete response and 5 a partial response. The elimination half-life of
rituximab was 445+/-361 h, and serum
rituximab levels were detectable at 3 months. In a phase II study, 90 patients with relapsed indolent B-NHL or
mantle cell lymphoma (MCL) were treated with infusions of
rituximab 375 mg/m(2) once weekly for four doses. The overall response rate in indolent B-NHL and MCL was 61% (37/61, 95% CI 47-73%) and 46% (6/13, 95% CI 19-75%), respectively. The median progression-free survival (PFS) was shorter in MCL patients, in those with extranodal disease, and in those who had received two or more prior
chemotherapy regimens ( P<0.01).
Rituximab retreatment was well tolerated in 13 patients with relapsed indolent B-NHL and there were no grade 3/4 nonhematologic toxicities. Partial response was observed in five (38%, 95% CI 14-68%) patients, and the median PFS after
retreatment was 5.1 months. In a single-agent phase II study of infusions of
rituximab 375 mg/m(2) once weekly for eight doses against relapsed aggressive B-NHL showed, 21 (37%, 95% CI 24-51%) of the 57 eligible patients responded. In conclusion,
rituximab is a highly effective agent in relapsed indolent and aggressive B-NHL and MCL with acceptable toxicities.
Yttrium-90 provides advantages over
iodine-131 because it delivers higher beta energy. In 2002, we initiated a feasibility study of yttrium-90-labeled
ibritumomab tiuxetan for relapsed indolent B-NHL in Japan.
Gemtuzumab ozogamicin (CMA-676) is a
calicheamicin-conjugated humanized anti-CD33
monoclonal antibody. Of 20 patients with relapsed or refractory
acute myeloid leukemia enrolled in a "bridging" phase I/II study, 7 showed an objective response. It is concluded that
monoclonal antibodies will have play a significant role in the treatment of
hematologic malignancies in the future.